Device for controlling electromagnetically operated valves

ABSTRACT

The present invention relates to a device for controlling electromagnetically operable valves of an electrohydraulic brake system for motor vehicles of the ‘brake-by-wire’ type having an electronic control or regulation unit that comprises at least one valve driver stage. In order to ensure maximum possible availability of the electronically controlled system functions, especially with a view to achieving a short stopping distance and a sufficient degree of vehicle stability regardless of the vehicle type or of whether the vehicle is loaded or unloaded, according to the present invention, the control and regulation unit includes two additional valve driver stages associated with which is a first and a second group of valves, the said driver stages being used to disable the first or the second group when malfunction occurs.

TECHNICAL FIELD

The present invention generally relates to a device for controllingvalves and more particularly relates to a device for controllingelectromagnetically operable valves of an electrohydraulic brake systemfor motor vehicles.

BACKGROUND OF THE INVENTION

International patent application WO 00/68053 discloses a brake system ofthis general type. The mentioned publication, however, does not provideany the failure probability of the actuation of the electromagneticallyoperable valves employed.

SUMMARY OF THE INVENTION

In view of the above, an object of the present invention is to disclosea device for actuating electromagnetically operable valves of anelectrohydraulic brake system of the type mentioned hereinabove, saiddevice ensuring maximum possible availability of the electronicallycontrolled system functions, especially with a view to achieving a shortstopping distance and a sufficient degree of vehicle stabilityregardless of the vehicle type or of whether the vehicle is loaded orunloaded.

This object is achieved by the present invention because the control andregulation unit includes two additional valve driver stages associatedwith which is a first and a second group of valves, the said driverstages isolating said group in addition from the supply voltage or mass,with a view to ensuring thereby the disabling of the first or the secondgroup also when malfunction occurs.

The present invention includes, in a first embodiment, a first valvedriver stage for driving the separating valves and for driving thepressure control valves respectively associated with a brake of a firstor a second vehicle axle. The present invention also includes a secondvalve driver stage for driving pressure-compensating valves and pressurecontrol valves associated with the other two wheel brakes of the firstor the second vehicle axle. The mentioned variant permits an electronicbrake pressure control on each of the four vehicle wheels.

A second embodiment of the present invention is that the first valvedriver stage is coupled to the separating valve of a first vehicle axle,the pressure-compensating valve of a second vehicle axle, and thepressure control valves being associated with respectively one brake ofthe first or the second vehicle axle, while the second valve driverstage is provided for the separating valve of the second vehicle axle,the pressure-compensating valve of the first vehicle axle, and thepressure control valves being associated with the other two brakes ofthe first or the second vehicle axle. This variant allows an electronicbrake pressure control of three wheels, while the master brake cylinderfurnishes the brake pressure for the wheel brake associated with thefourth wheel.

Finally, a third embodiment of the present invention includes couplingthe first valve driver stage to the separating valve and thepressure-compensating valve as well as the pressure control valves ofwheel brakes associated with a first vehicle axle, while the secondvalve driver stage is provided for the separating valve and thepressure-compensating valve as well as the pressure control valves ofwheel brakes associated with a second vehicle axle. This allocationallows an electronic brake pressure control of two wheels, while thepressure introduced by the driver into the master brake cylinder isapplied to the wheel brakes of the other wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified circuit diagram of a design of theelectrohydraulic brake system of the present invention.

FIG. 2 is a second alternative of actuating the electromagnetic valvesin an electrohydraulic brake system according to FIG. 1.

FIG. 3 is a third alternative of actuating the electromagnetic valves inan electrohydraulic brake system according to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electrohydraulic brake system illustrated in the drawingsessentially comprises a dual-circuit master brake cylinder or tandemmaster cylinder 2 that is operable by means of an actuating pedal 1,cooperates with a pedal travel simulator 3 and includes two pressurechambers isolated from one another and being in communication with anon-pressurized pressure fluid supply reservoir 4. Wheel brakes 7, 8e.g. associated with the rear axle are connected to the first pressurechamber (primary pressure chamber) by means of a closable firsthydraulic line 5, with wheel brake 7 being associated with the left rearwheel and wheel brake 8 being associated with the right rear wheel. Line5 is closed by means of a first separating valve 11, while in a lineportion 12 between the wheel brakes 7, 8 an electromagneticallyoperable, preferably normally open (NO) pressure-compensating valve 13is inserted which enables brake pressure control on each individualwheel, if required.

The second pressure chamber of the master brake cylinder 2, to which apressure sensor 15 can be connected, is connectable to the other pair ofwheel brakes 9, 10 associated with the front axle by way of a secondhydraulic line 6 closable by means of a second separating valve 14, withwheel brake 9 being associated with the left front wheel and wheel brake10 being associated with the right front wheel. Again, anelectromagnetically operable, preferably normally open (NO)pressure-compensating valve 19 is inserted into a line portion 16disposed between the wheel brakes 9, 10. Because the design of thehydraulic circuit connected to the second pressure chamber of the masterbrake cylinder 2 is identical with the brake circuit 11 that isexplained in the preceding description, it need not be discussed in thefollowing text.

A high-pressure accumulator 21 is used as the above-mentioned auxiliarypressure source, said accumulator being filled with pressure fluid underhigh pressure by a motor-and-pump assembly 20. The motor-and-pumpassembly 20 comprises a pump 23 driven by means of an electric motor 22as well as a pressure limiting valve 24 connected in parallel to saidpump 23. The suction side of the pump 23 is connected to theabove-mentioned pressure fluid supply reservoir 4 by way of a non-returnvalve. A pressure sensor 25 monitors the hydraulic filling pressure ofthe high-pressure accumulator 21 generated by the pump 23.

As can further be taken from the drawings, two electromagnetic, normallyclosed two-way/two-position directional control valves 17, 18 of analogoperation are associated with the wheel brakes 7, 8 of the vehicle rearaxle, said valves fulfilling the function of inlet valves that arerequired for electrohydraulically controlled braking operations and theinlet ports of which are connected to the above-mentioned high-pressureaccumulator 21. Further, the wheel brakes 7, 8 are connected to a thirdhydraulic line 39 by way of each one electromagnetic, normally closedtwo-way/two-position directional control valve or outlet valve 27, 28 ofanalog operation, said line 39 being in communication with thenon-pressurized pressure fluid supply reservoir 4, on the other hand.The hydraulic pressure prevailing in the wheel brakes 7, 8 is determinedby means of each one pressure sensor 30, 31. The wheel brakes 9, 10associated with the vehicle front axle cooperate similarly with valvepairs 34, 37 and 35, 38, respectively, with pressure control valves 34,35 fulfilling the function of the inlet valves and pressure controlvalves 37, 38 fulfilling the function of the outlet valves.

An electronic control unit 26 is used for the joint actuation of themotor-and-pump assembly 20 as well as the electromagnetic valves 11, 13,14, 17, 18, 19, 27, 28, 34, 35, 37, 38. The output signals of anactuating travel sensor 36, preferably of redundant design andcooperating with the actuating pedal 1, and of the above-mentionedpressure sensor 15 are sent as input signals to said control unit 26,thereby permitting a detection of the driver's deceleration demand.However, other means such as a force sensor sensing the actuating forceat the actuating pedal 1 may also be used for the detection of thedriver's deceleration demand. As further input quantities, the outputsignals of the pressure sensors 25, 30, 31 as well as the output signalsof wheel sensors (only represented) representative of the speed of thevehicle are sent to the electronic control unit 26.

As is indicated in FIG. 1 only schematically, the electronic controlunit 26 among others comprises a valve driver stage 29 and twoadditional valve driver stages 32, 33, the purpose of which is explainedin the following text.

To ensure maximum possible availability of the electronically controlledsystem functions of the illustrated electrohydraulic brake system, theabove-mentioned electromagnetically operable valves are subdivided intotwo groups and associated with the two additional valve driver stages32, 33. Thus, the group associated with the first additional valvedriver stage 32 is composed of the two separating valves 11, 14, thepressure control valves 34, 37 of the wheel brake 9 associated with theleft front wheel, and the pressure control valves 18, 28 of the wheelbrake 8 associated with the right rear wheel. In contrast thereto, thegroup associated with the second additional valve driver stage 33 iscomposed of the two pressure-compensating valves 13, 19, the pressurecontrol valves 35, 38 of the wheel brake 10 associated with the rightfront wheel as well as the pressure control valves 17, 27 of the wheelbrake 7 associated with the left rear wheels.

Upon failure of the first additional valve driver stage 32 or one of thedrivers of the associated valve group, said failure requiring subsequentclosure of the pressure-compensating valves 13, 19, it is still possibleto electronically control the brake pressures in the wheel brake 10associated with the right front wheel and the wheel brake 7 associatedwith the left rear wheel. A hydraulic through grip effected by thedriver by way of his/her actuating or pedal force acting upon the masterbrake cylinder 2 can produce the brake pressures in the wheel brake 9associated with the left front wheel and in the wheel brake 8 associatedwith the right rear wheel.

Upon failure of the second additional valve driver stage 33 or one ofthe drivers of the associated valve group, the two separating valves 11,14 can become closed. Since both pressure-compensating valves 13, 19remain open, the brake pressures in all four wheel brakes 7-10 can becontrolled electronically because the front axle is controlled by way ofthe valve pair 34, 37 and the rear axle by way of the valve pair 18, 28.

In the second example being shown in a greatly simplified view in FIG.2, the group associated with the first additional valve driver stage 32is composed of the separating valve 14 associated with the vehicle frontaxle, the pressure control valves 34, 37 of the wheel brake 9 associatedwith the left front wheel, the pressure-compensating valve 13 associatedwith the vehicle rear axle, as well as the pressure control valves 17,27 of the wheel brake 7 associated with the left rear wheel. In contrastthereto, the group associated with the second additional valve driverstage 33 is composed of the separating valves 11 associated with thevehicle rear axle, the pressure control valves 18, 28 of the wheel brake8 associated with the right rear wheel, the pressure-compensating valve19 associated with the vehicle front axle as well as the pressurecontrol valves 35, 38 of the wheel brake 10 associated with the rightfront wheel.

Upon failure of the first additional valve driver stage 32 or one of thedrivers of the associated valve group, said failure requiring subsequentclosure of the pressure-compensating valve 19 associated with thevehicle front axle and the separating valve 11 associated with thevehicle rear axle, it is still possible to electronically control thebrake pressures in the wheel brake 10 associated with the right frontwheel and the wheel brakes 7, 8 associated with the rear vehicle axle. Ahydraulic through grip effected by the driver by way of his/heractuating or pedal force acting upon the master brake cylinder 2 canproduce the brake pressure in the wheel brake 9 associated with the leftfront wheel.

Upon failure of the second additional valve driver stage 33 or one ofthe drivers of the associated valve group, said failure requiringsubsequent closure of the pressure-compensating valve 13 associated withthe vehicle rear axle and the separating valve 14 associated with thevehicle front axle, it is still possible to electronically control thebrake pressures in the wheel brake 7 associated with the left rear wheeland the wheel brakes 9, 10 associated with the vehicle front axle. Ahydraulic through grip effected by the driver by way of his/heractuating or pedal force acting upon the master brake cylinder 2 canproduce the brake pressure in the wheel brake 8 associated with theright rear wheel.

In the third example being shown in a greatly simplified view in FIG. 3,the group associated with the first additional valve driver stage 32 iscomposed of the separating valve 14 associated with the vehicle frontaxle, the pressure-compensating valve 19 associated with the vehiclefront axle as well as the pressure control valves 34, 37, 35, 38 of thewheel brakes 9, 10 associated with the vehicle front axle. In contrastthereto, the group associated with the second additional valve driverstage 33 is composed of the separating valve 11 associated with thevehicle rear axle, the pressure-compensating valve 13 associated withthe vehicle rear axle as well as the pressure control valves 17, 27, 18,28 associated with the wheel brakes 7, 8 of the vehicle rear axle.

Upon failure of the first additional valve driver stage 32 or one of thedrivers of the associated valve group, it is possible to electronicallycontrol the brake pressures in the wheel brakes 7, 8 associated with thevehicle rear axle without restrictions. A hydraulic through gripeffected by the driver by way of his/her actuating or pedal force actingupon the master brake cylinder 2 can produce the brake pressure in thewheel brakes 9, 10 associated with the vehicle front axle.

Upon failure of the second additional valve driver stage 33 or one ofthe drivers of the associated valve group, it is possible toelectronically control the brake pressures in the wheel brakes 9, 10associated with the vehicle front axle without restrictions. A hydraulicthrough grip effected by the driver by way of his/her actuating or pedalforce acting upon the master brake cylinder 2 can produce the brakepressure in the wheel brakes 7, 8 associated with the vehicle rear axle.

As can be taken from FIGS. 2 and 3, in particular, the additional valvedriver stages 32, 33 are connected in each case between thecorresponding valve group and the positive pole of a vehicle battery(only represented). It is, however, also feasible to interconnect theadditional valve driver stages 32, 33 between the corresponding valvegroup and the vehicle mass.

1. Device for controlling electromagnetically operable valves of anelectrohydraulic brake system for motor vehicles, comprising: a devicefor detecting a driver's request for deceleration, at least one of anemergency pressure generator or master brake cylinder operable by meansof a brake pedal, wherein said master cylinder includes at least onepressure chamber, and a non-pressurized pressure fluid supply reservoir,a hydraulic auxiliary pressure source whose pressure can be applied towheel brakes that are connectable to the master brake cylinder by way ofhydraulic connections closable by means of electromagnetically operableseparating valves, and associated with said separating valves areelectromagnetically operable pressure control valves that connect thewheel brakes to the pressure source in a pressure increase phase, andwhich are closed in a pressure maintaining phase and connect the wheelbrakes to the pressure fluid supply reservoir in a pressure reductionphase, electromagnetically operable pressure-compensating valves thatpermit a pressure compensation between the wheel brakes of a vehicleaxle, an electronic control and regulation unit for actuating theauxiliary pressure source, the separating valves, a control andregulation unit which includes first and second valve drivers associatedwith which is a first and a second group of valves, wherein said driverstages are used to disable the first or the second group, respectively,when a malfunction occurs, wherein the first valve driver is providedfor the separating valve of a first vehicle axle, thepressure-compensating valve of a second vehicle axle and the pressurecontrol valves being associated with respectively one brake of the firstor the second vehicle axle, while the second valve driver is providedfor the separating valve of the second vehicle axle, thepressure-compensating valve of the first vehicle axle and the pressurecontrol valves being associated with the other two brakes of the firstor the second vehicle axle.
 2. Device as claimed in claim 1, wherein thefirst valve driver stage cooperatively engages the separating valves andfor the pressure control valves respectively associated with a brake ofa first or a second vehicle axle, and wherein the second valve drivercooperatively engages the pressure-compensating valves and the pressurecontrol valves associated with two other wheel brakes of a first or asecond vehicle axle.
 3. Device as claimed in claim 1, wherein the firstvalve driver cooperatively engages the separating valve and thepressure-compensating valve as well as the pressure control valves ofwheel brakes associated with a first vehicle axle, while the secondvalve driver cooperatively engages the separating valve and thepressure-compensating valve as well as the pressure control valves ofwheel brakes associated with a second vehicle axle.